A (contracted) tech came to op check my mothers Nordyne M1MB nat gas, furnace found a faulty hotsurface ignitor which I replaced.

So now the inducer blows, the ignitor glows, I hear a clunk and (mostly blue) flame erupts (for 5-20 seconds), the main blower starts and then the flame goes out.Watching the status of the LEDs - red is constant and the amber blinks for randoms lengths of time. Although I cannot find anything like a flame sensor. Also the main blower keeps sending cold air into the mobile home while the ignitor starts glowing to start the cycle over.

The ignitor needed the old plug spliced on. I don't think I did anything to cause additional probs. The place is 10-12 yrs old. And I don't have alot of money to spend. I'm thinking control board or gas valve, but which? And how can I be sure?

You need to pay close attention to the amber flashes. That's the fault code. If you Google your furnace or check your manual, you'll get the fault and that will help narrow the problem. My guess (and I mean guess) it the inducer pressure switch (due to inducer motor issues) since it seems the furnace burner is not on long enough for the high limit to be the problem. Make sure all registers are open, all returns are clear and the filters are new.

Well go ahead and get a new circuit board and gas valve and after you do your heater still won't work. Furnaces are not a DIY project. Your best hope is to clean the flame sensor and keep your fingers crossed. If that does not work you might have to mess with the gas pressure but that is not something I would recommend so call a freaking company, Don't be cheap.